In the prior art one or several cranes are used to mount or change wind turbine components such as a blade or the whole rotor. The use of cranes is expensive, resulting in both a high economic cost and long response times resulting from lead time to schedule the availability of multiple cranes as well as of the down time resulting from the us of multiple cranes. Additionally, the use of cranes may be constrained by unfavorable weather, for example stormy or windy conditions. All these requirements may contribute to the wind turbine generator being out of service for more, increasing the down time therefore not generating energy, which implies important losses for the client who operates the wind farm.